Endocardial electrode

ABSTRACT

A medical electrode uniquely adapted for use as an endocardial electrode. An electrical conductor is encased in a material which is generally inert to body fluids and terminates at an exposed electrically conductive tip. A plurality of pliant tines extend from the electrode adjacent the tip and form an acute angle with the electrode body. Provision is made for holding the tines against the electrode body during insertion while allowing their release when the tip is in position. The released tines cooperate with the heart tissue, particularly the trabeculae found in the ventricles and the right atrial appendage, to maintain the electrode tip in position.

United States Patent [191 Citron et al.

[451 Sept. 2, 1975 ENDOCARDIAL ELECTRODE [75] Inventors: Paul Citron,New Brighton; Eugene A. Dickhudt, St. Paul, both of Minn.

[73] Assignee: Medtronic, Inc., Minneapolis, Minn.

[22] Filed: June 21, 1973 [21] Appl. No.: 372,269

[56] References Cited UNITED STATES PATENTS 2,854,983 10/1958 Baskin128/349 B 3,348,548 10/1967 Chardack..... 128/419 P 3,397,699 8/1968Kohl 128/243 3,516,410 6/1970 Hakim 128/350 R 3,568,659 3/1971Karnegis.... 128/243 3,608,555 9/1971 Greyson 128/348 3,717,151 2/1973Collett 128/350 R 3,719,190 3/1973 Avery.... 128/418 3,815,608 6/1974Spinosa et al. 128/349 R 3,835,864 9/1974 Rasor et al 128/418 X OTHERPUBLICATIONS Schaldach, New Pacemaker Electrodes, Trans: Am. Society ForArtificial Internal Organs, Vol. 17, 1971,

Wende et al., Neve intrakar dicle Schrittmacherelektrode, DeutscheMedizinisch-e Wochenschrift, Nr. 40, 2, Oct. 1970, pp. 2026-2028.

Pieper, Registration of Phesic Changes of Blood Flowby Means of CatheterType Flowmeter, Review of Sci. Instr., Vol. 29, No. 11, Nov. 1958, pp.965-967.

Primary ExaminerRichard A. Gaudet Assistant ExaminerLee S. CohenAttorney, Agent, or Firm-Lew Schwartz; Wayne A. Sivertson [57] ABSTRACTA medical electrode uniquely adapted for use as an endocardialelectrode. An electrical conductor is encased in a material which isgenerally inert to body fluids and terminates at an exposed electricallyconductive tip. A plurality of pliant tines extend from the electrodeadjacent the tip and form an acute angle with the electrode body.Provision is made for holding the tines against the electrode bodyduring insertion while allowing their release when the tip is inposition. The released tines cooperate with the heart tissue,particularly the trabeculae found in the ventricles and the right atrialappendage, to maintain the electrode tip in position.

17 Claims, 13 Drawing Figures PATENTEU 2975 3.902501 SHEET 1 UP 2 1ENDOCARDIAL ELECTRODE BACKGROUND OF, THE INVENTION Electricalstimulation of heart action is well-known and has been employed tocounter a variety of heart dysfunctions. Dependent upon the particulardysfunction, optimal placement of the electrical Contact point or pointsmay vary. However, optimal electrode placement has often been sacrificedto other considerations such as minimization of the surgical risk andreliability of the electrode securement. To date, the greatest number ofelectrodes have been ventricular electrodes with thetransvenous-endocardial approach coming into the fore in recent years.

The advantages of a reliable electrical contact with the atrium arewell-known. Such a contact would allow atrial pacing or atrialsynchronized pacing thereby preserving the contribution of the atrialcontraction in'the overall cardiac output. Additionally, an atrialcontact would be advantageously employed for arrhythmia management andother purposes which may not be accomplished through ventricularelectrical stimulation.

.For reasons well-known to those skilled in the art, the

greatest advantages can be obtained through an electrical contact withthe right atrium, the right atrial appendage providing a suitable site.

An attempt to accomplish transvenous or endocardial atrial pacing isdescribed in Smyth et. al. Permanent Transvenous Atrial Pacing, AnExperimental and Clinical Study, The Annals of Thoracic Surgery, VolumeII, No. 4, Apr. 19, 1971, pages 360-70. Here, a J-shaped catheter with aflange near the tip was inserted into the right atrial appendage througha transvenous approach. The catheter was straightened by the insertionof a stylet. When the stylet was with drawn, the catheter assumeditspreformed J shape for placement of the electrode tip in the atrialappendage. There was no attempt to artificially secure the electrode tipin position, the atrial trabeculae and shape of the catheter beingrelied upon to maintain it in location until the heart tissue itselfenveloped and fixed the tip. The metal parts of the catheter may beradiopaque to facilitate placement by viewing through fluoroscopy.

A sensing atrial endocardial electrode is described in Portsmann et.al., P Wave Synchronous Pacing Using Anchored Atrial Electrode ImplantedWithout Thoractomy", The American Journal of Cardiology, Volume 30, July1 l, 1972, pages 74-76. A .I-shaped applicator catheter was used todirect the electrode tip into the right atrial appendage. The electrodehowever, had two fine wire hooks positioned at its tip each ending in arelieving loop. The hooks were held back by the applicator catheter tospring out and anchor the electrode in the trabeculae of the rightatrial appendage whenthe electrode tip left the end of the applicatorcatheter.

In the applicator catheter technique described above, the applicatorcatheter was radiopaque so that it could be viewed as it was insertedinto the right atrial appendage. It is imperative with the double hooktip that the electrode be properly placed before the hooks are released.The placement was checked not only through fluoroscopy but also byextending the tip slightly beyond the end of the applicator catheter totake a threshold measurement. The tip had-to be extended sufficiently totake an accurate measurementwhile still I retaining the hooks within theapplicator catheter. Be-

SUMMARY OF THE PRESENT INVENTION The present invention provides anelectrode uniquely adapted for use as an atrial endocardial electrode.The electrode may be positioned in the right atrial appendage throughthe use of a .I-shaped catheter known to the prior art. Alternatively, aJ-shaped stylet may be employed which is held in a straightened positionby thewalls of the vein used to approach the heart, the stylet assumingits J-shape upon entry into the right atrium. A plurality of pliantnon-conductive tines are provided at the tip of the electrode tocooperate with the heart tissue, particularly the trabeculae found inthe right atrial appendage, to maintain the electrode tip in electricalcontact with the heart tissue while allowing a removal of the electrodeshould that prove necessary. Provision is also made for holding thetines against the electrode body during insertion while allowing theirrelease when the tip is in position and after a test thresholdmeasurement. Although the electrode is discussed inthe context of theright atrial appendage, it is suitable for use in any portion of theheart having the requisite cooperating tissue and may be employed aseither a sensing or pacing electrode.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a preferred embodiment ofthe present invention.

FIG. 2 shows a cross section of the preferred embodiment of FIG. Itakenalong the line 22 in FIG. 1.

FIG. 3 shows a cross section of another preferred embodiment taken-alongthe line 2-2 in FIG. 1.

FIG. 4 illustrates apparatus which may be used with the preferredembodiment of FIG. I.

FIG. 5 shows acomponentof another preferred embodiment of the presentinvention.

FIG. 6 shows'a preferred embodiment of the present inventionwhichutilizes the component of FIG. 5, the tines being in a restrainedposition.

FIG. 7 shows the embodiment. of FIG. 6 with the tines unrestrained.

FIG. '8 shows another preferred embodiment of the present invention.

FIG. 9 shows still another preferred embodiment of the presentinvention.

FIG. 10 shows a further preferred embodiment of the present invention.

FIG. 11 shows a portion of the preferred embodiment of FIG.- 10.

FIG. 12 shows a portion of the preferred embodiment of FIG. 10.

FIG. 13 shows anadditional preferred embodiment of the presentinvention.

DETAILED. DESCRIPTION GFTHE DRAWINGS tive tip 11 and a plurality oftines 12 extending at an acute angle from the body member from aposition adjacent the tip 11. The electrically conductive tip 11 may beof any material suitable for the environment; platinum-iridium, forexample. The tines 12 are ofa pliant material which is generally inertto body fluids; silicone rubber or polyurethane, for example. The tines12 may be attached to the body member 10 in any convenient manner. Forexample, the tines may extend from, and be unitary with, a disc 13 whichdisc is held in position between the body member 10 and tip 11.Alternatively, the member 13 may be in the form of a ring which liesover either the body member 10 or tip 11 and is adhered thereto in anyconvenient manner. The tines 12 may take any angle with the body member10, their purpose being to cooperate with the body tissue, particularlythe trabeculae of the right atrial appendage, to maintain the tip 11 inelectrical contact with the body tissue. It can be seen that an acuteangle formed by the tines l2 and the body member 10 will have thegreatest tendency to push against and become involved with thecooperating trabeculae and maintain the tip 11 in electrical contact. Ithas been found, that an angle of approximately 45 maintains thenecessary electrical contact is a very efficient manner. Further, anynumber of tines may be used; three having proven to be adequate in mostsituations.

Referring now to FIG. 2 wherein there is shown a cross section of apreferred embodiment of the body member 10 of FIG. 1 taken along theline 22. In this embodiment, an elongated electrical conductor 15 runssubstantially the length of the body member 10 and makes electricalcontact with the tip 11. The conductor 15 is encased within a catheter16 of a material which is generally inert to body fluids.

It is desirable that the catheter conductor combination be made asflexible as possible. To accomplish this purpose while providing thenecessary rigidity for insertion of the electrode, a stylet lumen 19 isprovided, the stylet being within the lumen 19 during insertion of theelectrode and being withdrawn after placement is accomplished. In apreferred embodiment, the stylet which is placed into the lumen 19 has aJ configuration similar to that of the prior art applicator catheters.During insertion, the stylet is maintained in a straightenedconfiguration by the walls of the vessel through which insertion isaccomplished. When the electrode tip reaches the atrium, the styletassumes its J configuration thereby allowing an easy insertion into theappendage. When the placement of the electrode tip is accomplished, thestylet is withdrawn. In this embodiment, the electrical conductor can beof any known type, one preferred form being a multistrand wire ofplatinum, for example, commonly referred to as tinsel wire. I

A second preferred form for the body member 10 is illustrated in FIG. 3.Here, the electrical conductor is a coiled member 17 which again runssubstantially the length of the body member 10. The coil 17 is encasedin a catheter 16 substantially identical to that shown in FIG. 2. Thecentral portion of the coil 17 is left at least partially void to formalumen 18 for the insertion of a stylet, the stylet serving essentiallythe same function in this embodiment as in the embodiment of FIG. 2.Further, in both the embodiments of FIG. 2 and FIG. 3, the lumens l9 and18 may be lined with Teflon or any other appropriate material tofacilitate the insertion and removal of the stylet.

Referring now to FIG. 4, there is again shown an electrode body portion10 this time at the end farthest from the tip 11. In some applications,a pin type connection to an external stimulator or sensing device isdesired. For this purpose, the body portion 10 commonly has an enlargedsegment 20 from which extends the connecting pin 21. If it is desired toinsert the electrode through the use of the J-shaped applicator catheterknown to the prior art, the catheter must be made suffieiently large toslide back over the enlarged portion 20 or, alternatively, some othersystem for removal of the catheter must be provided. Here, theapplicator catheter is shown at 22 of a size not sufficiently large tobe withdrawn over the enlarged portion 20. A cutting tool 23 is shownadjacent the enlarged portion 20 and extending forward of the enlargedportion with a wedge 24 and a knife blade 25. The cutting tool 23 may beseparate from the electrode body 10 or may be attached thereto in anyconvenient manner. In operation, the wedge portion 24 slips under theedge of the applicator catheter 22 and, as the applicator catheter 22 isdrawn toward the cutting tool 23, the wedge will direct the catheter 22into contact with the knife blade which will then cut and separate itthus allowing the removal of the applicator catheter over the enlargedportion 20.

The electrode shown in the embodiment of FIG. 1 may be successfullyinserted into the right atrial appendage through a transvenous approachusing the stylet technique of either FIGS. 2 or 3 or the .I-shapedapplicator catheter technique. In the applicator catheter technique, thetines 12 are not exposed during insertion. In the stylet technique ofeither FIGS. 2 or 3, however, the tines are non-restrained or extendedduring the entire operation. Although the electrode may be successfullypositioned in this condition, it is found that the blood flow tends todraw the electrode tip into the ventrical. For this reason, some meansof restraining the tines during insertion is desirable.

Referring now to FIG. 5, there is shown a balloon catheter similar tothe balloon catheters used for other applications. Specifically, thecatheter body 10 has a portion 30 which is inflatable from an end 32.The inflation is accomplished through a lumen similar to the styletlumen 19 and 18 of FIGS. 2 and 3 respectively. Indeed, the inflation canbe accomplished through the stylet lumens 19 and 18, the lumens beingmade sufficiently large to accomodate the stylet while allowing apassage for air to inflate the balloon. The ballooning feature of theelectrode body 10 may be accomplished in any known manner. Referring nowto FIG. 6, there is shown an electrode having a body 10 and a tip 11 asdescribed with reference to the embodiment of FIG. 1. The body 10 iscomposed of a balloon catheter as illustrated in FIG. 5 with theballooning or inflatable part lying adjacent the tip 1 l. A hold downshroud 31 is positioned near the tip 11 and is adapted to receive atleast the ends of the tines 12 to restrain them in a position whereinthey overlie the inflatable portion 30 of the electrode body 10. Withthe tines in this restrained position, a stylet may be inserted into alumen such as that illustrated in FIGS. 2 or 3 and the electrodeinserted through a transvenous approach without any interference fromthe extended tines. When the electrode tip is believed to be in anacceptable position as viewed by fluoroscopy, a test measurement can bemade. If the site of the electrode tip proves satisfactory, the balloon30 can be inflated from the end of the electrode still outside the bodycausing the tines to withdraw from the shroud 31 and extend into theirnormal unrestrained position as illustrated in FIG. 7. With the tinesfreed from the shroud 31 the inflating pressure can be released and theballoon 30 will deflate to a normal configuration. The shroud 31 maytake any shape which can accept at least the end portions of the tines12. A ring which is attached to the body by spaced tethers is an exampleof an obvious modification of the shroud 31.

An alternative shroud to the shroud 31 of FIG. 7 is illustrated at 35 inFIG. 8. This shroud 35 again is adapted to accept at least the endportion of the tines 12 to restrain them in a position wherein theyoverlie the body of the electrode 10. A line 36 is attached to theshroud 35 at 37, and when the tip is properly positioned, a force on theline 36 will cause the shroud 35 to withdraw thus freeing the tines 12to assume their extended unrestrained position. A similar approach isillustrated in FIG. 9 wherein a stylet 40 is shown having a coiledportion 41 which coiled portion is wrapped around the tines causing themto lie flat against the body member 10. Again, when the tip 11 isproperly positioned, the stylet will be withdrawn thereby freeing thetines for interaction with the trabeculae of the right atrial appendage,for example.

Referring now to FIG. 10, there is shown another preferred embodiment ofthe present invention. Specifically, there is shown an electrode body 10composed of a connecting portion 50, a central portion 51 and an endportion 52 which lies between the tip 11 and the shroud 53. The crosssection of the central portion 51 may be as illustrated in FIG. 3. Thatis, the electrical conductor is a coiled member 17 having a void lumenforming central portion 18, the conductor extending from the tip 11 backto the connecting portion 50. The connecting portion 50 is similar tothat illustrated in FIG. 4 with the connecting pin 54 making anelectrical contact with the electrical conductor 17 and having a lumencoincident with the lumen 18 of the conductor 17. With thisconfiguration, it is possible to insert a stylet 55 through the end ofthe connecting pin 54 to abut the tip 11. Inasmuch as the electricalconductor is a coiled member it can be stretched or elongated byapplying a pressure against the tip 11 with the stylet 55. Since theelectrical conductor is typically uniform throughout its length, thelocation at which the elec trode body will give or elongate can becontrolled to the durometer or diameter of the electrode body, or both.For reasons to be explained more fully below, it is desired that theportion 52 of the electrode body 10 give before the central portion 51or the connecting portion 50. Therefore, the portion 52 is illustratedas having a smaller diameter than either the central portion 51 or theconnecting portion 50. Alternatively, the material comprising theportion 52 may have a lower durometer than either of the other portionsof the electrode body 10 or it may have a lower durometer and diameter,as desired.

FIG. 11 illustrates the embodiment of FIG. 10 with the tines 12 havingat least their ends restrained by the shroud 53 in a mannersubstantially identical to that illustrated in FIG. 6. With the tines intheir restrained position, the electrode can be inserted and positionedand, when a proper positioning is obtained as described above, thestylet is forced against the tip 11 causing the portion 52 to stretch asillustrated in FIG. 12 thereby releasing the tines 12 from the shroud53. With the tines released, the stylet is removed thereby allowing theportion 52 to assume its normal shape as illustrated in phantom at FIG.12.

As stated with regard to the shroud 31 of FIGS. 6 and 7, the shroud 53of FIGS. 10-12 may take the form of a ring connected to the electrodebody by means of a plurality of tethers. Such a ring shroud isillustrated at in FIG. 13. As can be seen, the shroud 60 has a ring or adoughnut configuration and is held in place by means of tethers 61 whichperform essentially as the spokes of a wheel, the tethers 61 beingpositioned so as not to interfere with the restraining and release ofthe tines 12.

From the above, it can be seen that the present invention provides a newmedical electrode uniquely adapted for use as an endocardial electrode.The electrode provides means for cooperating with the heart tissue,particularly the trabeculae of the ventricles and right atrialappendage, to provide an artificial fixation until such time as anatural fixation has occurred. The tines are of a pliant material whichis sufficiently rigid to accomplish their purpose without having thesnapping action and sharp points attendant in the prior art devices.Further, the present invention provides a system for positioning theelectrode and making any necessary test measurements prior to its beingfinally posi tioned, the position of the tip with regard to theinserting devices being much less critical in the present invention thanin the prior art devices because the tines may be selectively releasedindependently of the insertion device.

Obviously, many modifications and variations of the present inventionare possible in light of the above teaching. An example of such amodification would be to make the body member 10 or the tines 12, orboth, radiopaque to facilitate the positioning by observation of theelectrode through Xray., fluoroscopy, etc. We have found that this canbe accomplished through impregnation with carbon, barium sulfate orTantalum. Of course, any suitable substance and method will beacceptable for this purpose. It is therefore to be understood that,within the scope of the appended claims, the invention may be practicedotherwise than as specifically described.

What is claimed is:

1. In an endocardial lead of the type having an electrical conductorencased in a material which is generally inert to body fluids, theconductor terminating at an exposed electrically conductive electrodetip, the improvement which comprises:

nonconducting tine means extending from said encasing material and awayfrom said tip from a location adjacent said tip for cooperating withheart tissue, to hold the tip in position, said tine means forming agenerally acute angle with said encasing material and being entirely ofa pliant material having sufficient rigidity to maintain said angle whensaid tine means are unrestrained, but sufficiently pliant to preventpenetration of said heart tissue, said pliant material being generallyinert to body fluids.

2. The lead of claim 1 wherein the improvement fur ther comprises meansexternal to said encasing mate- 7 rial for releasably restraining saidtinc means in a position overlying said encasing material.

3. The lead of claim 2 wherein said restraining means comprises shroudmeans for accepting at least the end portion of said tine means.

4. The lead of claim 3 wherein said restraining means further comprisemeans cooperating with said shroud means for effecting the release ofsaid tine means at a point spaced from said shroud means.

5. The lead of claim 3 wherein the improvement further comprises:

inflatable means underlying said tine means when said tine means are insaid restrained position; and means spaced from said inflatable meansfor selectively inflating said inflatable means.

6. The lead of claim 4 wherein said tine means are non-metallic.

7. An endocardial lead which comprises:

elongated electrically conductive means;

flexible catheter means surrounding said electrically conductive meansand having a lumen substantially parallel to and coextensive with saidelectrically conductive means;

electrically conductive tip means at one end of said catheter means andelectrically connected to said electrically conductive means; and

nonconducting tine means extending from said catheter means and awayfrom said tip from a point adjacent said tip means for cooperation withheart tissue, to hold the tip in position, said tine means forming agenerally acute angle with said catheter means and being entirely of apliant material having sufficient rigidity to maintain said angle whensaid tine means are unrestrained, but sufficiently pliant to preventpenetration of said heart tissue, said pliant material being generallyinert to body fluids.

8. The lead of claim 7 further comprising means for releasablerestraining said tines in a position wherein they overlie said cathetermeans.

9. The lead of claim 8 wherein said restraining means comprises shroudmeans for accepting at least the end portion of said tine means. 7

10. The lead of claim 9 wherein said restraining means further comprisesmeans cooperating with said shroud means for effecting the release ofsaid tine means at a point spaced from said shroud means.

1 l. The lead of claim 9 wherein said catheter means comprises a ballooncatheter, the balloon underlying the tines when the tines are in therestrained position.

12. The lead of claim 11 wherein said elongated electrically conductivemeans comprises a coiled electrical conductor having a void centralportion, said lumen coinciding with said void central portion.

13. The lead of claim 11 wherein said elongated electrically conductivemeans is positioned substantially at the center of the cross section ofsaid catheter means and said lumen lies off the center of said crosssection.

14. In a medical lead of the type in which an electrical conductor ispositioned within a catheter and terminates at an exposed electricallyconductive electrode tip, the improvement which comprises:

nonconducting tine means including a plurality of tines each extendingfrom said catheter and away from said tip from a point adjacent said tipand forming an acute angle with said catheter for cooperating with hearttissue to hold the tip in position, said tine means being entirely of apliant material having sufficient rigidity to maintain said angle whensaid tine means are unrestrained, but sufficiently pliant to preventpenetration of said heart tissue; means for releasably restraining saidtine means in a position wherein said tine means overlie said catheter;and I means underlying said tine means when said tine means are in saidrestrained position and inflatable from a point spaced from saidrestraining means for releasing said tine means from said restrainingmeans upon inflation.

15. The medical lead of-claim 14 wherein the angle formed by said tinemeans and said catheter is approximately 45.

16. The medical lead of claim 14 wherein said pliant tine means materialcomprises a material which is relatively inert to body fluids, at leasta portion of said material being radiopaque.

17. The medical lead of claim 16 wherein the radiopaque material portionis a material treated with a material selected from the group consistingof carbon, barium sulfate or Tantalum.

1. In an endocardial lead of the type having an electrical conductorencased in a material which is generally inert to body fluids, theconductor terminating at an exposed electrically conductive electrodetip, the improvement which comprises: nonconducting tine means extendingfrom said encasing material and away from said tip from a locationadjacent said tip for cooperating with heart tissue, to hold the tip inposition, said tine means forming a generally acute angle with saidencasing material and being entirely of a pliant material havingsufficient rigidity to maintain said angle when said tine means areunrestrained, but sufficiently pliant to prevent penetration of saidheart tissue, said pliant material being generally inert to body fluids.2. The lead of claim 1 wherein the improvement further comprises meansexternal to said encasing material for releasably restraining said tinemeans in a position overlying said encasing material.
 3. The lead ofclaim 2 wherein said restraining means comprises shroud means foraccepting at least the end portion of said tine means.
 4. The lead ofclaim 3 wherein said restraining means further comprise meanscooperating with said shroud means for effecting the release of saidtine means at a point spaced from said shroud means.
 5. The lead ofclaim 3 wherein the improvement further comprises: inflatable meansunderlying said tine means when said tine means are in said restrainedposition; and means spaced from said inflatable means for selectivelyinflating said inflatable means.
 6. The lead of claim 4 wherein saidtine means are non-metallic.
 7. An endocardial lead which comprises:elongated electrically conductive means; flexible catheter meanssurrounding said electrically conductive means and having a lumensubstantially parallel to and coextensive with said electricallyconductive means; electrically conductive tip means at one end of saidcatheter means and electrically connected to said electricallyconductive means; and nonconducting tine means extending from saidcatheter means And away from said tip from a point adjacent said tipmeans for cooperation with heart tissue, to hold the tip in position,said tine means forming a generally acute angle with said catheter meansand being entirely of a pliant material having sufficient rigidity tomaintain said angle when said tine means are unrestrained, butsufficiently pliant to prevent penetration of said heart tissue, saidpliant material being generally inert to body fluids.
 8. The lead ofclaim 7 further comprising means for releasable restraining said tinesin a position wherein they overlie said catheter means.
 9. The lead ofclaim 8 wherein said restraining means comprises shroud means foraccepting at least the end portion of said tine means.
 10. The lead ofclaim 9 wherein said restraining means further comprises meanscooperating with said shroud means for effecting the release of saidtine means at a point spaced from said shroud means.
 11. The lead ofclaim 9 wherein said catheter means comprises a balloon catheter, theballoon underlying the tines when the tines are in the restrainedposition.
 12. The lead of claim 11 wherein said elongated electricallyconductive means comprises a coiled electrical conductor having a voidcentral portion, said lumen coinciding with said void central portion.13. The lead of claim 11 wherein said elongated electrically conductivemeans is positioned substantially at the center of the cross section ofsaid catheter means and said lumen lies off the center of said crosssection.
 14. In a medical lead of the type in which an electricalconductor is positioned within a catheter and terminates at an exposedelectrically conductive electrode tip, the improvement which comprises:nonconducting tine means including a plurality of tines each extendingfrom said catheter and away from said tip from a point adjacent said tipand forming an acute angle with said catheter for cooperating with hearttissue to hold the tip in position, said tine means being entirely of apliant material having sufficient rigidity to maintain said angle whensaid tine means are unrestrained, but sufficiently pliant to preventpenetration of said heart tissue; means for releasably restraining saidtine means in a position wherein said tine means overlie said catheter;and means underlying said tine means when said tine means are in saidrestrained position and inflatable from a point spaced from saidrestraining means for releasing said tine means from said restrainingmeans upon inflation.
 15. The medical lead of claim 14 wherein the angleformed by said tine means and said catheter is approximately 45*. 16.The medical lead of claim 14 wherein said pliant tine means materialcomprises a material which is relatively inert to body fluids, at leasta portion of said material being radiopaque.
 17. The medical lead ofclaim 16 wherein the radiopaque material portion is a material treatedwith a material selected from the group consisting of carbon, bariumsulfate or Tantalum.